1. Field of the Invention
The present invention relates to an optical detecting device utilizing an optical component to condense the light beam, and more particularly, to a multi-segment optical component capable of increasing signal-to-noise ratio and a related optical detecting device utilizing the multi-segment optical component.
2. Description of the Prior Art
Please refer to FIG. 1 and FIG. 2. FIG. 1 is a diagram of an optical detecting device 50 in prior art. FIG. 2 is a sectional view of a conventional Fresnel lens. The optical detecting device 50 utilizes a light emitting component 52 to output an optical detecting signal, the optical detecting signal is projected onto and reflected from an external object 56 to be received by an optical detecting component 54, and the optical detecting device 50 acquires information of the external object 56 by analyzing the reflected optical detecting signal. The external object 56 includes an epidermal layer 561, a dermis layer 562 and a vessel 563. As the external object 56 does not contact against a touch region of the optical detecting device 50, the optical detecting component 54 receives an epidermal scattering signal S1, a dermis scattering signal S2 and a vessel scattering signal S3. The dermis scattering signal S2 and the vessel scattering signal S3 is helpful to acquire the wanted information of the external object 56, and the epidermal scattering signal S1 is noise which decreases detection accuracy about the external object 56 analyzed by the optical detecting device 50.
The conventional Fresnel lens 58 is disposed above the light emitting component 52 to increase quantity of the optical detecting signal. The conventional Fresnel lens 58 is mainly composed of a central lens portion 581 and a plurality of lateral lens portions 582. A curvature radius r1 of the central lens portion 581 is substantially equal to curvature radii r2, r3, r4 of the lateral lens portions 582. A curvature center O1 of the central lens portion 581 and curvature centers O2, O3, O4 of the lateral lens portions 582 overlap a symmetry axis S of the central lens portion 581. The conventional Fresnel lens 58 cannot overcome noise interference resulted from the epidermal scattering signal S1; therefore, design of an optical detecting device capable of effectively eliminating the epidermal scattering signal to increase detection accuracy is an important issue in the related optical detection industry.